In regard to specified personal identification based on a fingerprint, various methods for inputting ridge-and-recess patterns of a fingerprint into a computer as an image by using laser beams and analyzing the same have been developed in place of an older visual identifying method.
A number of methods have been proposed as a method for detecting a fingerprint. As in (Patent Document 1) and (Patent Document 2), an optical method for directly picking up a ridge-and-recess pattern of a fingerprint into an image sensor by combining differences in the scattering angle between a ridge and a recess of the fingerprint with all the reflection conditions and a method for extracting a ridge-and-recess pattern of a fingerprint by utilizing a semiconductor sensor that detects a difference in electrolytic distribution on a contact surface have been used in practice.
In addition, as in (Patent Document 3), a method for extracting a venous pattern of a fingertip and palm by utilizing a near-infrared light and for identifying a specified person has been proposed and have been commercialized.
On the other hand, when a laser beam is irradiated onto a living body, the intensity distribution of the reflected and scattering light dynamically changes due to moving scattering particles such as blood cells, and forms laser speckles (that is, a random speckle pattern) on the image-forming surface. It has been known that bloodstream distribution of capillary vessels in the vicinity of the surface of a living body may be made visible as an image by detecting the laser speckle pattern by an image sensor on the image-forming surface, and displaying the change with the passage of time (hereinafter merely called “time change”) of the laser speckle pattern in a two-dimensional map by quantifying the time change at respective pixels.
The present applicant disclose a method and an apparatus for measuring subcutaneous bloodstream and eyeground bloodstream and displaying the same as a two-dimensional bloodstream map in (Patent Document 4) through (Patent Document 9).
(Patent Document 1) Japanese Published Unexamined Patent Application No. H5-73666
(Patent Document 2) Japanese Published Unexamined Patent Application No. H8-16752
(Patent Document 3) Japanese Published Unexamined Patent Application No. 2003-331268
(Patent Document 4) Japanese Published Examined Patent Application No. H5-28133
(Patent Document 5) Japanese Published Examined Patent Application No. H5-28134
(Patent Document 6) Japanese Published Unexamined Patent Application No. H4-242628
(Patent Document 7) Japanese Published Unexamined Patent Application No. H8-112262
(Patent Document 8) Japanese Published Unexamined Patent Application No. 2003-164431
(Patent Document 9) Japanese Published Unexamined Patent Application No. 2003-186041